4x4Wire TrailTalk

Surging is back....ARGH!!!!

Posted By: Boyota

Surging is back....ARGH!!!! - 06/15/06 03:02 AM

'86 non turbo 4 runner

Well that surging problem has re appeared after more than two weeks of it not happening at all.

I don't think surging describes it properly.It just cuts out. It doesn't stumble or pulse.

It operates normally up to a certain RPM, (unknown because I don't have a tach, but i can guestimate it's the same by ear)
Then when it reaches that point, the engine ceases to respond.It totally cuts out, but no dash lights come on. No trouble codes either

If I press the throttle-nothing, If I flutter the throttle-nothing. Let off the gas-nothing. But the exhaust odor changes dramatically (4-runner has that back window in-draft when down)
Untill it coasts back down to another common rpm then the engine "catches" and operates normally, BUt... ONLY in the range up to the cut out point, which is the same in all gears.

Strange thing is that the throttle doesn't respond within the operating range once it cuts out untill it drops down to the "catch" point.
In other words, to drive 46 mph I have to be in 5th gear(thats the actual reading, not adjusted for 31's) Fourth only operates up to about 39 mph then cuts out so -I shift to 5th. So my range in 5th is from 39 to 46 mph. The throttle responds fine and the engine fires just fine in that range BUT once I go over 46 mph, all operation ceases, I just coast, even with the throttle held open at that speed or fully open or anything. Now on the coast down to 39mph the throttle still doesn't respond at 45, 44, 43, 42 etc. Untill I hit 39 mph, then it's all back.

I was refering to it as surging because when its parked and the engines cuts out, the idle drops much faster then when in a driving gear and it suges- like pumping the throttle every 2 seconds under normal operating conditions

It's not the TPS (Tried three different units) or the AFM
(another three different units), I've bypassed the VSV to the fuel pressure regulator, topped off the radiator and burped it, took off the EGR, checked the plugs. Replaced the fuel filter.

i think it's the ignition system somewhere.
What could behave like that in the ignition?
I've tested the resistancees in the coil and they were okay, but the problem is intermitant. The problem shows lasts for a few hours, sometimes days, then goes away. I'm going to try another coil tomorrow(see my next post about coil questions)

Still stumped. Need some sugestions

I know I posted alot on this back a few weeks ago but
Sometimes distance lends perspective
Posted By: Davepet

Re: Surging is back....ARGH!!!! - 06/15/06 09:18 AM

But the exhaust odor changes dramatically (4-runner has that back window in-draft when down)

How does it change? More gas smell, less gas smell??
i think it's the ignition system somewhere.

Seems unlikely to me. If it's cutting out at a specific RPM it is more likely that the computer is getting a faulty signal from one of the sending units, or, in the worst case, that the computer itself is bad & in either case is cutting off the fuel at that RPM.

Most like is a bad sender, but afraid I don't know the system well enough to tell you exactly where to look, but in general,I'd start looking at senders that can in normal operation, trigger a fuel off situation (eg: if the TPS shows your foot off the pedal & the RPMs are above a minimum limit, fuel gets shut off).

Posted By: foxtrapper

Re: Surging is back....ARGH!!!! - 06/15/06 12:12 PM

There is a maximum RPM cut out in the ECU. Found it on one of mine attempting to blow the engine up while having a tantrum. Checked the others later (non-tantrum mode), and they all have it. Up around 7000 rpm as I recall. The engine would cut, catch, cut, catch, rapid cycling to prevent the rpm from going over this limit.

So it is possible that you're somehow running into this with a defective ECU. Though I rather doubt this is the case from your description.

In your case, I rather suspect you've got a wire that is barely making contact. Ignition most likely. And when the engine reaches X rpm, the position of the engine, or the air flow from the cooling fan, or other such thing, causes the wire to lose contact.

Chased a similar problem for quite a while once with a Triumph. Engine would just die. Open the hood and the engine would run fine. Close the hood and drive, engine would die. In this case it was the hood catching the harness and pulling it slightly out of the ignition module. Interesting diagnostic job.
Posted By: Anonymous

Re: Surging is back....ARGH!!!! - 06/15/06 12:49 PM

You say it just stumbles not dies, right? It sounds like an fuel pump problem since you have checked/changed all the other stuff. Are you still getting any codes? I can't think of any sensors tied to the ECU that would send a "cut fuel" signal, other than the AFM or the TPS. I know you have changed the filter but have you changed the fuel pump? My wife had an Oldsmobile and for over a year it had the exact same problem that you are describing. I couldn't figure it out, the dealer couldn't either. It only did it at random but it basically went into limp mode. It would still run but only at idle once it happened. The more gas you gave it the rougher the idle. If you let it sit there a min. or two, it would be fine for a few days. Well the fuel pump finally completely quit (on the highway) and once it was changed, it never happened again.
Posted By: TexJeff87

Re: Surging is back....ARGH!!!! - 06/15/06 02:12 PM

I'm voting for the fuel pump first and the ECU second. You can get a used ECU for about $100, least that's what I paid when I took mine swimming a few years back... <img src="/forums/images/graemlins/zombie.gif" alt="" />

No codes, eh?

Tell you what...I'm sure you have a bud with the same motor..swap ECU's with him and see what happens. Won't take 10 minutes...
Posted By: Boyota

Re: Surging is back....ARGH!!!! - 06/15/06 06:22 PM

Ok, here's my logic on this

The fuel pump constantly pumps, always holds a steady pressure, just pumps one set PSI.

At the fuel rail is the pressure regulator that holds the required pressure in the rail for the injectors to use, any thing extra gets dumped back to the tank?
Is this correct?

It seems to me that a pump going out would cause this "cut out" at random intervals, not like I described at very regular and specific intervals.

Back when this first began happening, I really though it was the filter restricting fuel to the rail, and once i'd reach a certain fuel consumption at that magical rpm, it would die out untill the pressure redeveloped in the rail and it could feed the injectors.

It feels like when you run out of gas and the first thing you feel, especially when accelerating, is the severe inertia loss, sort of throws you forward, no throttle response untill you splash some back to the pump and it jerks back to acceleration, but my problem is very rhythmic, predictable.

If i had the funds, believe me i'd go pull a CPU and buy a pump and a coil, but I am very tight budgeted these days and unfortunately have just moved and have no buds with similar trucks anywhere near me. And all the pick n pulls around here are severly picked. <img src="/forums/images/graemlins/angry.gif" alt="" />
Posted By: 4Crawler

Re: Surging is back....ARGH!!!! - 06/15/06 06:26 PM

The fuel pump does run all the time but the FPR varies the fuel pressure basec upon engine load, usually in the range of 28-35 psi. A fuel pressure gauge on the rail would tell you if the pressure drops when the loss of power occurs. Might also check and clean all the engine and body ground connections. Might be an intermittent electrical issue with a loose or dirty connection that only shows up at certain temps or engine RPMs.
Posted By: TOY4ICK

Re: Surging is back....ARGH!!!! - 06/15/06 08:04 PM

When I've seen this problem before, it was caused by a problem in the TPS circuit. If the truck thinks it is at idle (idle switch closed on TPS), it will cut the fuel at a predetermined upper limit RPM. Once the RPM drops down to a set lower level, fuel is allowed again. Is your TPS set up properly? Roger's site has a pretty clear description of the adjustment procedure. You may have to check the signal at the computer. If there is a short to ground on the idle circuit in the harness, it won't matter what the TPS says. Good luck.
Posted By: Boyota

Re: Surging is back....ARGH!!!! - 06/15/06 08:55 PM

I'd really lean towards the AFM or the TPS too, BUT, I have the same issue with any combination of the three units I have for each component. I did resistance tests on the harness via the FSM and everything loked ok. I recall unbolting a few ground connections polishing them up and reconnecting.

One thing re: the TPS
I described above how I have functionability in a certain range, and in this range I can accelerate slowly up to the cut off point,
I can move the throttle to different positions while accelerating to that cut off, and feel the different responses in the motor, which tells me that the TPS is sending a good signal.
If I could lock the throttle to any open position, be it a light throttle or heavy throttle, say sticking feeler guages bwetween the throttle stop and adjuster screw space on the throttle body, it revs to that cut off and dies then drops rpm, catches and revs to cut off.....

Just thinking out loud.

I'm going to go pull the ecu and voltmeter the FSM flow chart tests....Again

I'm not quite clear on
If there is a short to ground on the idle circuit in the harness, it won't matter what the TPS says.

But if the flow chart tests show anything questionable I WILL BE BACK.

Thanks for the suggestions. <img src="/forums/images/graemlins/kewl.gif" alt="" />
Posted By: Boyota

Re: Surging is back....ARGH!!!! - 06/15/06 09:05 PM

So it's not doing it now so there is really no point in running diagnostics.

If it was going to do it, would do it right after I start it, no warm up, first throttle. So it being a warm up issue isn't the case here. It still may show up just down the road, or later tonight after driving it all day. Just no way of pinning down an environmental issue.

Where are all the body and engine ground points?
Especially regarding this issue? I just dont want to miss any.
Posted By: TOY4ICK

Re: Surging is back....ARGH!!!! - 06/15/06 09:26 PM

Resistance is futile, voltage is a much better indicator of what is happening.

The TPS has a sensor circuit and a switch inside. There are four wires: E2 - ground; IDL - idle circuit (on or off); VTA - variable voltage signal (varies with throttle position); VCC - 5 volt reference signal. If the idle switch in the TPS is closed (E2 and IDL connected), the computer will disregard the variable throttle signal. If the IDL wire between the TPS and computer is shorted to ground anywhere, the computer sees this as the switch being closed and implements its idle speed limiting strategy. I would check for ground at pin 6 (or maybe it is 8 - whichever has the black/white wire) at the 18 pin connector (the middle one) of the computer with the throttle open. You should be able to see the signal change as the throttle is opened and closed. If this circuit is always grounded, then you have narrowed down your problem. I hope this makes some sense and I haven't just made things more confusing. I'll try to check back later and see how you are doing.
Posted By: TOY4ICK

Re: Surging is back....ARGH!!!! - 06/15/06 09:41 PM

DOH! On my 4Runner, the IDL circuit wire at the computer is only black and it is in the #6 pin position. With the key on, simply backprobe the wire with the ground lead of your meter at the connector and put the positive lead at a 12 volt source. You should read battery voltage until you press down on the gas pedal, then there should be 0 volts.
Posted By: 4Crawler

Re: Surging is back....ARGH!!!! - 06/15/06 10:02 PM

Where are all the body and engine ground points?
Especially regarding this issue? I just dont want to miss any.

The FSM shows them all, cab is behind the driver's side kick panel, and probably one over by the ECU in the passenger side kick panel area. Engine is back of head, and around the intake, battery, fender and frame.
Posted By: Boyota

Re: Surging is back....ARGH!!!! - 06/16/06 06:17 PM

Ran perfect yesterday, runs fine today.
Hopefully it stays like this untill the weekend. If you've read any of the other threads, It only does it once a week and usually in the most unwated times, like on the way to a big catering gig. Never when just shopping or casually driving.
Tomorrow I'll pull the ecu and do a volt check, then keep it out for when it decides to cut out on me. Had it sitting on the passenger floor for a week last time I did tests.

I hate on again off again problems. REALLY hard to diagnose.
I'll check in after the tests <img src="/forums/images/graemlins/kewl.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" />
Posted By: Boyota

Re: Surging is back....ARGH!!!! - 06/16/06 11:03 PM

It started again, then stopped, so I'm going to hook the voltmeter to the ECU and leave it there so I can do a real time diagnostic.

Hey, I have three meters,
any other places that may be helpful for me to leave hooked while operating under normal conditions? <img src="/forums/images/graemlins/confused.gif" alt="" />
Posted By: solarcrew

Re: Surging is back....ARGH!!!! - 06/20/06 05:36 AM

<img src="/forums/images/graemlins/scared.gif" alt="" /> Get the truck running and shake the injector wiring harness that runs below and thru the intake plennum.There's a crimp connector in this harness that can come apart and cause intermittent problems.Hope this helps. <img src="/forums/images/graemlins/cheers.gif" alt="" />
Posted By: Boyota

Re: Surging is back....ARGH!!!! - 06/20/06 05:51 AM

Tried shaking the wires with no reaction.

Pulled the whole harness last summer, stripped the casing, soldered those pesky crimps even though they were tightly intact, and soldered them properly, clean tight solders too

(anyone remember the sevice guy who posted on the miltary soldering guide via a Navy(?) solderer last August or so?)

I've done alot of harness shifting trying to eliminate or reproduce this problem.

Maybe I'll pull that whole harness again just for kicks n giggles cuz I'm gona go crazy <img src="/forums/images/graemlins/drunk.gif" alt="" />
Posted By: Staceman

Re: Surging is back....ARGH!!!! - 06/20/06 02:46 PM

I had the same intermittant shut down/stumbling along with no error codes as you described. New (used) fuel pump in the tank did the trick. Always seemed to run fine while just cruising, but once I let off the gas while slowing down, that's when mine would slow down until it died. Pumping the throttle while this was going on had no response what-so-ever.
Posted By: engnbldr

Re: Surging is back....ARGH!!!! - 06/20/06 03:29 PM

>>>*Sounds like an old Dodge I had once. I chased electrical and fuel filters, etc, not really that tough on those old rigs.

Finally it hit me that it was just uphill under load or at higher speeds.

As speed picks up, volume of fuel moved picks up. Turned out to be some water in the tank, the pump would move the fuel at slower speeds and begin to pick up water at higher speeds.

*Just a thought....*EB
Posted By: toyrunner

Re: Surging is back....ARGH!!!! - 06/20/06 07:35 PM

I had a 1977 Celica, 22R that when driving steady, ran fine. If I tried anything else, higher rpm, any slight incline, it cut out. I diagnosed everything under the sun <img src="/forums/images/graemlins/confused.gif" alt="" />
and finally changed the fuel filter. That thing had so much sand in it!
Drove me crazy, that car <img src="/forums/images/graemlins/baby.gif" alt="" />
Ran like new after the filter change.
Just a thought.
Posted By: Boyota

Re: Surging is back....ARGH!!!! - 06/21/06 04:46 AM

Fuel pump $22 at PnP, That's the next try for sure.

Got a tach installed this weekend and I can tell it was at about 1800 rpm's that it was cutting out, every gear, even parked.

Now I haven't had the prob for about two weeks then BAM, steady cruising about ten miles down brand new bumpless highway and it cut. Went away after about five miles of dealin' wit it. Then it came back that evening after about 75 miles of driving in between. <img src="/forums/images/graemlins/angry.gif" alt="" />

Now it seems it's been gone (for about two weeks) since I removed the cap, cleaned the terminals and the rotor but also did a few other things,

So this weekend I replaced it with a new brass contact set.

Been running it W/ my voltmeter hooked to the IDL circut on the ECU, but ya know the dang thing won't cut untill I get sick of the mess and put the ECU back and replace the kick cover.

So I'm done untill it cuts again. <img src="/forums/images/graemlins/ignore.gif" alt="" /> Then off to get the fuel pump. Can't diagnose anything untill it's in that mode.

Looking at 110 here in a few days so I think I'll concentrate on charging that air conditioning <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> that'll be a good test for the peel n seal soundproofing. <img src="/forums/images/graemlins/notooth.gif" alt="" />
Posted By: bigchota

Re: Surging is back....ARGH!!!! - 11/05/06 02:44 PM

Check out my earlier post on similar problem
Surging Idle Problem & Fix FYI
#825449 - 12/22/05 07:33 AM
Posted By: mnwolftrack

Re: Surging is back....ARGH!!!! - 11/06/06 04:00 AM

I didn't get a chance to read through all the previous responses but figured I'd chime in. I know of two ways to make a very similar problem happen. The first is excessively high idle speed adjustment, and when the brake pedal is stepped on, the surging begins. If the brake is released, the surging goes away. The second way I know of to make this happen is low coolant or an air bubble. I routinely have this surging happen after I've flushed coolant or installed a new engine and I'm waiting for the engine to warm up and the t-stat to open. Now, while neither of these issues may directly be related to your problem, they may help. If there's an air bubble at the engine temp sensor, it will cause the surging. Have you checked or replaced your temp sensor? Second, the computer knows the brakes are applied and cuts the injectors until the RPM's drop down (below around 1300RPM). The theory is that if you are braking, you are not stepping on the gas and don't need fuel. There's a basic switch on the brake pedal assembly that's responsible for turning the tailight's brake light bulbs on, but the wire does not run straight from the pedal to the bulbs. The wire goes through the computer, and that's how it knows the brakes are applied.

So, a few thoughts that come to mind are 1) malfunctioning computer, 2) improperly adjusted brake pedal switch 3) malfunctioning temp sensor.

Whatever the issue is, it appears to be an all or nothing deal. Meaning, it's not just affecting one cylinder such as would be the case with a bad wire or plug. It's affecting everything, and it's symptoms are very similar to an air bubble at the temp sensor or high idle.
Posted By: kewlynx

Re: Surging is back....ARGH!!!! - 11/06/06 04:14 AM

Loosen your gas cap and see how it drives; might not be ventilating properly.

??? Think of how fluids flow out of a container that have the vent cap left on; same deal.

Something cheap to eliminate for a change.
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